The present invention relates to a computer system having a recording/reproducing device which uses a DVD-RAM or the like as a recording medium. More particularly, the invention relates to a computer system that can record data in the most desirable manner even if a logical block and a record block differ in size.
This application is based on Japanese Patent Application No. 09-253713 filed on Sep. 18, 1997, the content of which is cited herein by reference.
Generally, a recording/reproducing device (recording media device) can be connected to or incorporated in a personal computer or a portable computer, so that it may be used as an external memory.
The file system (i.e., the computer), which manages the writing of data into and the reading of data from an external memory, has two types of data blocks. The first type is a logical block, which is a logical unit of data. The second type is a record block, which is a unit of data to be written into or read from the recording medium provided in the external memory.
In the actual data-writing process, not only the data managed in the form of the logical block, but also error correction codes and the like are recorded on the recording medium. This means that the record block has the same size as a unit of data to be subjected error correction. The record block must be identified in the file system so that the file system may efficiently access to the recording media device. To this end, the recording media device is designed to access the file system in the logical block, which corresponds to the record block. The file system manages data such as files, in units of logical blocks, efficiently exchanging data with the recording medium.
As indicated above, the logical block which the file system manages and the record block which is a unit of data to be written into or read from the recording medium by the recording media device have the same size in most cases. In some file systems, the size of the logical block may be defined to the multiple size of the record block. This is because the number of logical blocks which the file system can manage is limited, and the number of logical blocks must be reduced.
Manufacture of recording media of a large storage capacity has been started, thanks to the recent developed technique of increasing recording density. Streams of image data and streams of sound data are recorded on a recording medium which has a large storage capacity. It is better to perform error correction on such a recording medium which has a large storage capacity in units of larger data blocks than in units of relatively small data blocks as conventionally employed. The reason is that the overhead is smaller when the data is corrected in units of larger blocks, ultimately enhancing the storage efficiency. Therefore, the size of the record block may be larger on a recording medium of large storage capacity.
In some cases, however, the size of the logical block cannot be larger corresponding to the size of the record block. If the logical blocks are made as large as the record blocks, they may no longer be compatible with the logical blocks on the conventional recording medium, or may no longer conform to the applied standards. For example, the EEC (Error Correcting Code) blocks (i.e., record blocks) on a DVD (Digital Versatile Disc) have a size of 32 KB, whereas the logical blocks on the DVD have a size of 2 KB as is designated on the basis of the standards. In other words, an error correction code (ECC) is added to every 16 logical blocks. When the logical blocks differ in size from the record blocks as in this case, the speed of accessing the recording medium and reliability may inevitably decrease.